1. Field of the Invention
This invention relates broadly to a radiation detection apparatus and method. More particularly, it relates to an optical attenuation monitor system and method which employs light irradiation techniques to detect accumulation of optically attenuating objects on the outside surface of an electro-optical instrument housing viewing window. The term "light radiation" used herein refers to the visible, infrared and ultraviolet light regions of the electromagnetic radiation spectrum.
2. Description of the Prior Art
In metals producing and rolling mill installations it is commonplace to encounter severe dusty and dirty environments where reliable measurements should be made by electro-optical instruments associated therewith. Because of increased automation and production speed there is an ever increasing need for more accurate and reliable product temperature and dimensional measurements that must be made in these severe environments.
Generally, such measurements are made by electro-optical instruments located in a suitable housing behind a viewing window. For example, light radiation must pass through the viewing window in the form of variable intensity beam to a radiation pyrometer or as a variable image pattern to an electro-optical dimensional gage inside the housing which measures the temperature or dimension of the product located outside of the instrument housing. Invariably, light-scattering optically attenuating objects, such as dust, dirt, scale, pits and scratches, will accumulate on the outside surface of the viewing window. This accumulation attenuates light radiation transmitted through the window and produces an unaccountable optical error which reduces the accuracy and reliability of readings of precision electro-optical instruments located inside the instrument housing.
Heretofore, the outside surface condition of an instrument housing viewing window was either ignored, overlooked or corrected only by routine maintenance of the associated production facility. In a few instances when the viewing window was cleaned, it was done improperly leaving some of the light-scattering optically attenuating objects on the viewing window. An alternative to these procedures is to require more extensive maintenance on a more frequent basis. Until now this would be the recommended procedure because the precision electro-optical instruments inside the housing have no way of knowing about or correcting for optical attenuation errors due to accumulation on the outside of the viewing window.